SEA 235, Operator'S Manual

Page: 12 / 104

GENERAL OPERATIONS
7
DEMAND TUNE
When the tuner senses a high VSWR, it will attempt to match the antenna
automatically during transmit. The Demand Tune function signals the tuner to
undergo a complete tune cycle even with an acceptable VSWR. This may be
needed on those rare occasions when the “TND” indicator does not appear or
when the operator suspects the match could be better. For the Demand Tune
function to operate, the SEA 1612C or SEA 1635 tuner must have the ‘DTN’
terminal connected to the SEA 235’s rear panel accessory connector P3 pin 10
(DMD TUNE). The ‘TUNER’ option in the radio’s “SETUP” menu must also
be programmed to “TNR ON”. Better tunes may occur using Demand Tune.
To Demand Tune, key the radio by holding the
PTT button on the microphone down, then
press and release
to start the tune
cycle.
The “TND” indicator will turn off, the “LOW”
indicator will turn on and the radio will show
“TUNING”.
When the tuner has successfully completed the
match, the “LOW” indicator will disappear as
the “TND” indicator appears and the display
will show the VSWR. Release the microphone
PTT.
In the event that the tuner can not find a match
in 15 seconds, the radio will stop transmitting
and the display will read “NO TUNE”.
When tuning with voice, “HI VSWR” will
occasionally be displayed until the tune cycle
has successfully completed the antenna match.
NOISE BLANKER OPERATION
Use the key to toggle the noise
blanker on / off. The “NB” indicator shows the
noise blanker is on. The noise blanker will
help reduce impulse noise that may be caused
by on board equipment such as a bilge pump or
refrigerator compressor.
TX LOW
TX LOW
TX LOW
TX
TND
NB TND
FNC
NB
SEND